The present invention relates to the fabrication of engineering design models, and more particularly to the construction of a structure for the representation of ducting in such models.
It has become a widely accepted engineering practice to fabricate highly accurate and detailed scale models of large and complex installations, such as chemical processing plants, refineries, and nuclear power generating stations. The use of such models began in the late nineteen forties or early nineteen fifties, the earliest models being relatively crude, formed largely of wood and brass wire. Ultimately, it was realized that more detailed models could provide a highly effective tool for the design of these installations, in many instances replacing, instead of merely supplementing the voluminous drawings that were more conventional. More specifically, the inherent limitations of representing a complex three-dimensional structure on a two-dimensional surface could be escaped by using the models, and the frequently encountered unwelcome discovery on the construction site that structures shown on two different drawings interfered with each other could be eliminated almost completely. It also became apparent that the optimum lay-out of three-dimensionally interrelated ducting and piping can be discovered more easily and quickly by actually designing the installation as the model was built. The proper order of construction could also be determined from the model, and persons who could not visualize the finished installation from the drawings could readily comprehend the model. As the usefulness and cost saving significance of engineering design models has become widely recognized, there has been a continuing demand for more accurate and sophisticated models.
Modern design models are cut into easily managed segments, each supported on a separate table and capable of being moved and re-assembled at the construction site or other location where they are most useful. They are color coded and labeled to aid in understanding the manner in which the installation functions, also utilizing transparent components so that the interior structure is not hidden. Transparent piping and ducting is sometimes color coded by coloring an edge of each segment, the color being transmitted and recognizable throughout.
To meet the need for accuracy of detail in model engineering design models, professional model builders currently maintain inventories of pre-fabricated components including, for example, beams, cross beams, ladders, stairways, boilers, condensers, valves, piping and ducting. Typical heating, ventilating and air conditioning ducting of rectangular cross section imposes especially burdensome inventory requirements because it requires a great variety of sizes, shapes and colors. Ducting also tends to be heavy and therefore expensive because its relatively large cross section consumes excessive quantities of plastic. The cost of injection molding large sizes of ducting is often prohibitive and at times the plastic may not be available.
One proposed solution to the problem of representing ducting has been the use of plastic foam as a construction material. Foam, however, is easily damaged by small quantities of the solvent used to weld joints on the models, and it is difficult to avoid unintended solvent contact. Moreover, foam is relatively porous and therefore cannot be readily painted for labeling or color coding.